Multiobjective optimization of the antioxidant activities of horse mackerel hydrolysates produced with protease mixtures

Fish protein hydrolysates (FPH) from horse mackerel were produced by employing an enzyme mixture of subtilisin and trypsin. The antioxidant activity of fish hydrolysates (DPPH scavenging activity, Fe²⁺ chelating activity and Fe³⁺ reducing power) was modelled as a function of the operating conditions for the hydrolysis (i.e. protein concentration, temperature and composition of the enzyme mixture). The antioxidant activities showed different behavior depending on whether their controlling pathway was the transference of electrons/protons (i.e. DPPH scavenging activity and Fe³⁺ reducing power) or metal chelation. In the first case, the antioxidant activities increased with the decrease of substrate concentration and temperature when pure trypsin (DPPH scavenging activity) or a mixture of enzymes (Fe³⁺ reducing capacity) was employed. Contrarily, hydrolysates showed higher Fe²⁺ chelating activities at moderate concentration and high temperature (i.e. 5 g/L and 55 °C) employing solely subtilisin. The conflictive behavior among the antioxidant properties suggested using a multiobjective optimization technique. The ε-constraint method was chosen for this purpose. This approach allows determining the most adequate operational conditions for producing hydrolysate with a specific antioxidant profile which is the first approximation to the production of taylor-made antioxidant hydrolysates.